During audio communication, to increase a capacity of a communications system, usually, a transmit end first encodes each frame of original audio signal to be transmitted, and then transmits the audio signal. The audio signal is compressed by means of encoding. After receiving the signal, a receive end decodes the received signal, and restores the original audio signal. To implement maximum compression on an audio signal, different types of encoding manners are used for different types of audio signals. In other approaches, when an audio signal is a speech signal, a continuous encoding manner is usually used, that is, each frame of speech signal is encoded, when an audio signal is a noise signal, a discontinuous encoding manner is usually used to encode the noise signal, that is, one frame of noise signal is encoded every several frames of noise signals. For example, a noise signal is encoded every six frames. After the first frame of noise signal is encoded, the second frame of noise signal to the seventh frame of noise signal is not encoded, and the eighth frame of noise signal is encoded. The second frame to the seventh frame is six No_Data frames. Further, the audio signal is a mono audio signal.
With the development of audio communications technologies, an audio communications system further has a special communication manner, stereo communication. That the stereo communication is dual channel communication is used as an example. The two channels include a first channel and a second channel. A transmit end obtains, according to an nth-frame speech signal on the first channel and an nth-frame speech signal on the second channel, a stereo parameter used to mix the nth-frame speech signal on the first channel and the nth-frame speech signal on the second channel into one frame of downmixed signal, where the downmixed signal is a mono signal. Then, the transmit end mixes the nth-frame speech signals on the two channels into one frame of downmixed signal, where n is a positive integer greater than 0, then encodes the frame of downmixed signal, and finally, sends the encoded downmixed signal and the stereo parameter to a receive end. After receiving the encoded downmixed signal and the stereo parameter, the receive end decodes the encoded downmixed signal, and restores the downmixed signal to a dual channel signal according to the stereo parameter. Compared with a transmission manner in which each frame of speech signal on the two channels is encoded, in this transmission manner, a quantity of transmitted bits is greatly reduced, implementing compression.
However, when a noise signal is transmitted during the stereo communication, if a same encoding manner is used as that for a speech signal, and a discontinuous encoding manner used in mono is directly applied to the stereo communication, the receive end cannot restore the noise signal, leading to poor subjective experience of a user of the receive end.